Satellite radioterminal communications systems and methods are widely used for radioterminal communications. Satellite radioterminal communications systems and methods generally employ at least one space-based component, such as one or more satellites, that is/are configured to wirelessly communicate with a plurality of satellite radioterminals.
A satellite radioterminal communications system or method may utilize a single satellite antenna pattern (beam or cell) covering an entire service region served by the system. Alternatively or in combination with the above, in cellular satellite radioterminal communications systems and methods, multiple satellite antenna patterns (beams or cells) are provided, each of which can serve a substantially distinct service region in an overall service region, to collectively provide service to the overall service region. Thus, a cellular architecture that is similar to that used in conventional terrestrial cellular radioterminal systems and methods can be implemented in cellular satellite-based systems and methods. The satellite typically communicates with radioterminals over a bidirectional communications pathway, with radioterminal communications signals being communicated from the satellite to the radioterminal over a downlink or forward link (also referred to as forward service link), and from the radioterminal to the satellite over an uplink or return link (also referred to as return service link). In some cases, such as, for example, in broadcasting, the satellite may communicate information to one or more radioterminals unidirectionally.
The overall design and operation of cellular satellite radioterminal systems and methods are well known to those having skill in the art, and need not be described further herein. Moreover, as used herein, the term “radioterminal” includes cellular and/or satellite radiotelephones with or without a multi-line display; Personal Communications System (PCS) terminals that may combine a radioterminal with data processing, facsimile and/or data communications capabilities; Personal Digital Assistants (PDA) that can include a radio frequency transceiver and/or a pager, Internet/Intranet access, Web browser, organizer, calendar and/or a global positioning system (GPS) receiver; and/or conventional laptop and/or palmtop computers or other appliances, which include a radio frequency transceiver. A radioterminal also may be referred to herein as a “radiotelephone,” a “mobile terminal,” a “user device,” a “wireless transmitter,” a “wireless receiver,” a “transceiver” or simply as a “terminal”. As used herein, the term(s) “radioterminal,” “radiotelephone,” “mobile terminal,” “user device,” “wireless transmitter,” “wireless receiver,” “transceiver” and/or “terminal” also include(s) any other radiating user device, equipment and/or source that may have time-varying or fixed geographic coordinates and/or may be portable, transportable, installed in a vehicle (aeronautical, maritime, or land-based) and/or situated and/or configured to operate locally and/or in a distributed fashion over one or more terrestrial and/or extra-terrestrial location(s). Furthermore, as used herein, the term “space-based component” or “space-based system” includes one or more satellites at any orbit (geostationary, substantially geostationary, medium earth orbit, low earth orbit, etc.) and/or one or more other objects and/or platforms (e.g., airplanes, balloons, unmanned vehicles, space crafts, missiles, etc.) that has/have a trajectory above the earth at any altitude.
The above description has focused on communications between the satellite and the radioterminals. However, cellular satellite communications systems and methods also generally employ a bidirectional feeder link for communications between one or more satellite gateway(s) and the satellite(s). The bidirectional feeder link includes a forward feeder link from the gateway(s) to the satellite(s) and a return feeder link from the satellite(s) to the gateway(s). The forward feeder link and the return feeder link each uses one or more carriers.
A satellite generally includes at least one feeder link amplifier that is used to amplify a return feeder link signal prior to transmitting the return feeder link signal from the satellite to the satellite gateway(s). The satellite may also inadvertently receive a level of interference, over its return service links, from emissions of one or more terrestrial networks and/or satellite terminals of other operators (e.g., Inmarsat), and the satellite may not be configured to separate and/or discard the level of interference. Thus, the satellite may inadvertently form a return feeder link signal that includes at least some of the level of interference as well as one or more desired signals.
The feeder link amplifier may be operatively configured to not exceed a maximum level of output power in order to, for example, maintain a desired level of linearity. As such, as the level of interference increases, an amount of amplification applied to a desired signal may be reduced. This reduction is referred to as “power robbing.”
Power robbing may be reduced by increasing a capability (e.g., size) of the feeder link amplifier to accommodate a desired level of amplification of one or more desired signals along with the level of interference while maintaining a desired level of linearity. Unfortunately, an increased capability amplifier (e.g., a larger amplifier) may undesirably increase cost, power consumption and/or weight of a satellite. Power robbing also may be decreased by increasing an aperture of the satellite's feeder link antenna(s). However, increasing the aperture of the satellite's feeder link antenna(s) may also undesirably increase the size, cost and/or weight of the satellite.